Examines a surprisingly simple application of unidirectional security that supports essentially risk-free MLS (multi-level security). It is an unusual environment because security rules can be absolutely enforced. Not only security violations, but also multi-level communication handshaking and most downgrading is not simply disallowed, but prevented. Experiments conducted using hardware multiple single-level nodes interconnected by unidirectional links show how this environment can be a practical alternative to software-enforced security. When we can adapt to this environment, the benefits include near-absolute strength, high performance and low cost. It seems particularly applicable to legacy systems because it is almost independent of pre-existing hardware and software.